Counterfeiting next year's coins and prospering (7,5)

I believe the answer is:

forging ahead

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'prospering' is the definition.
Although both the answer and definition are present participle verbs, I cannot understand how they can define each other.

'counterfeiting next year's coins' is the wordplay.
'counterfeiting' becomes 'forging' ('forge' can be a synonym of 'counterfeit').
'next year's coins' becomes 'ahead' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'forging'+'ahead'='FORGING AHEAD'

'and' acts as a link.

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I've seen this clue in The Globe and Mail.

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